It is common practice in industrial flexible automation assembly lines to have a work piece on a work piece carrier move along a track from one work station to another. At different work stations along the track, the work piece carrier will stop to allow an operation to be performed on the work piece. A system of code storing devices attached to the work piece carrier and code reading devices (sensing heads) placed along the track near each work station indicates to the flexible automation system the work stations at which an operation is to be performed.
Each sensing head has a plurality of sensors arranged in a particular alignment to detect any one of a plurality of codes stored in a code storing device placed on the work piece carrier. The sensing head is normally constructed by hard wiring the sensors to a printed circuit board, placing the sensors inside a housing in the particular alignment required, and then filling the housing with a potting compound to permanently fix the sensors in their preset alignment. The potted sensors cannot be removed from the housing. If a sensor should fail or should a different type (N.C., N.O., PNP, NPN, DC, or AC) of sensor be required in any one of the sensor positions, a new sensing head must be purchased. This is a significant cost to the customer in labor, equipment down time, and additional sensing heads.